This invention relates to the feeder system of a so-called ground linear motor in which a linear motor is supplied with driving power from equipment on the ground.
An arrangement is known in which a linear motor has a stator provided on the ground and a moving element provided on a vehicle, just as a rotary motor is provided with a stator and a rotor, with a propulsion force or regenerative braking force generated between the stator and the moving element being utilized to run a train. However, a striking difference between a linear motor and a rotary motor is that whereas the stator and rotor in the rotory motor are in full opposition to each other at all times, only a portion of the stator in the linear motor opposes the moving element at all times.
For the foregoing reason, the armature coil which is the ground stator in an LSM (linear synchronous motor) serves to generate a propulsion force only in the portion of the coil opposed by the LSM magnetic field on the vehicle. Even if a current is continuously passed through the other armature coil portion on the ground, this merely increases the power loss and invites a rise in the temperature of the ground armature coil and excessive expenditures. A feeder section changeover system is employed in order to prevent such wasteful power loss.
As shown in FIGS. 1(a) through 1(c), a ground armature coil is electrically divided at fixed distances and current is passed only through the section of the ground armature coil at which the train is present. More specifically, as shown in FIG. 1(a), when a vehicle VH is at the section A of the ground armature coil, a frequency converter FCA feeds the ground armature coil section A with electricity via a feeder LA. Then, when the vehicle VH passes from section A to section B of the ground armature coil, as shown in FIG. 1(b), a frequency converter FCB feeds the ground armature coil section B with electricity via a feeder LB, so that section B is fed in addition to section A of the ground armature coil. When the vehicle VH makes a complete transition to the section B of the ground armature coil, as shown in FIG. 1(c), feed of electricity is cut off from the ground armature coil section A and electricity continues to be fed solely to the section B of the ground armature coil.
In order to prevent a fluctuation from developing in the vehicle propulsion force when the sections of the ground armature coil are changed over in this manner, it is necessary to alternately connect the sections A and B of the ground armature coil to the feeders LA and LB, provide the two frequency converters FCA, FCB and successively change over the feed of electricity in conformance with the movement of the vehicle VH.
With this feeder system, therefore, the fact that two frequency converters FCA, FCB are required results in a complicated construction as well as higher installation and maintenance costs.